A year ago we decided that colored coins is the name of a concept, rather than a specific protocol. So many different protocols can exist.

It isn't necessarily a bad thing. Different protocols have different traits, and it is up to "the market" to decide which is the optimal one.

I expect that eventually one protocol will dominate, but we also can end up with different protocols being used for different things. It isn't a problem to implement several protocols in one wallet applications.

Stupid question: is this 100% compatible with the coinprism implementation of colored coins?

No, it isn't compatible with CoinPrism. Although we might add support for CoinPrism colors some time later.

So it's Betamax vs. VHS all over again?

If I understand it correctly, Coinprism uses a centralized server, while chromawallet does not.

My understanding was that the centralized server aspect of Coinprism was incidental. I was pretty sure what they did could work in a decentralized way but just nobody has released a wallet code for it yet (but they're working on it).

Interesting... would be great if we could all agree on one colored coin protocol, but I'm just a casual observer here...